* device/lib/pic/libm: NEW, added math library functions

[fw/sdcc] / device / lib / pic / libm / atanf.c

diff --git a/device/lib/pic/libm/atanf.c b/device/lib/pic/libm/atanf.c
new file mode 100644 (file)
index 0000000..5192e2a
--- /dev/null
+++ b/device/lib/pic/libm/atanf.c
@@ -0,0 +1,74 @@
+/*  atanf.c: Computes arctan of a 32-bit float as outlined in [1]
+
+    Copyright (C) 2001, 2002  Jesus Calvino-Fraga, jesusc@ieee.org 
+
+    This library is free software; you can redistribute it and/or
+    modify it under the terms of the GNU Lesser General Public
+    License as published by the Free Software Foundation; either
+    version 2.1 of the License, or (at your option) any later version.
+
+    This library is distributed in the hope that it will be useful,
+    but WITHOUT ANY WARRANTY; without even the implied warranty of
+    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+    Lesser General Public License for more details.
+
+    You should have received a copy of the GNU Lesser General Public
+    License along with this library; if not, write to the Free Software
+    Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307 USA */
+
+/* [1] William James Cody and W.  M.  Waite.  _Software manual for the
+   elementary functions_, Englewood Cliffs, N.J.:Prentice-Hall, 1980. */
+
+/* Version 1.0 - Initial release */
+
+/*
+** $Id: atanf.c 3654 2005-01-24 10:38:53Z vrokas $
+*/
+
+#include <math.h>
+#include <errno.h>
+
+#define P0 -0.4708325141E+0
+#define P1 -0.5090958253E-1
+#define Q0  0.1412500740E+1
+#define Q1  0.1000000000E+1
+
+#define P(g,f) ((P1*g+P0)*g*f)
+#define Q(g) (Q1*g+Q0)
+
+#define K1  0.2679491924 /* 2-sqrt(3) */
+#define K2  0.7320508076 /* sqrt(3)-1 */
+#define K3  1.7320508076 /* sqrt(3)   */
+
+float atanf(const float x) _MATH_REENTRANT
+{
+    float f, r, g;
+    int n=0;
+    static float a[]={  0.0, 0.5235987756, 1.5707963268, 1.0471975512 };
+
+    f=fabsf(x);
+    if(f>1.0)
+    {
+        f=1.0/f;
+        n=2;
+    }
+    if(f>K1)
+    {
+        f=((K2*f-1.0)+f)/(K3+f);
+        // What it is actually wanted is this more accurate formula,
+        // but SDCC optimizes it and then it does not work:
+        // f=(((K2*f-0.5)-0.5)+f)/(K3+f);
+        n++;
+    }
+    if(fabsf(f)<EPS) r=f;
+    else
+    {
+        g=f*f;
+        r=f+P(g,f)/Q(g);
+    }
+    if(n>1) r=-r;
+    r+=a[n];
+    if(x<0.0) r=-r;
+    return r;
+}
+